Question

一个C#中的问题，提示当前上下文中不存在名称“conn“，这个conn是我建立的一个对象。代码如下。

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Data.SqlClient;

namespace Eg3_4
{
public partial class FrmConnState : Form
{
public FrmConnState()
{
SqlConnection conn= new SqlConnection("serve=(local);database=NoteTaking;Integrated Security=sspi");
InitializeComponent();
}

private void btnOpen_Click(object sender, EventArgs e)
{
conn.Open();
txtConnState.Text = conn.State.ToString();
btnOpen.Enabled = false;
btnClose.Enabled = true;

}

private void btnClose_Click(object sender, EventArgs e)
{
conn.Close();
txtConnState.Text = conn.State.ToString();
btnOpen.Enabled = true;
btnClose.Enabled = false;

}
}
}

Answer 1

你的conn得定义为字段
你定义在方法里面，
当然不能全局用了
public FrmConnState()
{
SqlConnection conn= new SqlConnection("serve=(local);database=NoteTaking;Integrated Security=sspi");
InitializeComponent();
}

把这个改为
SqlConnection conn= new SqlConnection("serve=(local);database=NoteTaking;Integrated Security=sspi");
public FrmConnState() {

InitializeComponent();
}